Clinical laboratory instruments are utilized by hospitals, clinical laboratories, doctors' offices and the like for analyzing body fluids, such as whole blood, serum or plasma, in order to diagnose diseases. Since the chemistries are somewhat similar for related areas, such as the veterinary diagnostic area and the analysis of food components, these instruments have a broader usefulness, but, by far, their largest market is in the human clinical chemistry area. In order to utilize these instruments, a broad range of reagents are necessary. First, there are control materials (or reference materials) which are used to confirm that the instrument is working properly. These are similar to the materials that are being analyzed, usually of known composition and analyzed in a manner similar to the way specimens are analyzed. Second, there are calibrators, which are used to calibrate the system, i.e., used to draw a calibration curve for the analyte. Third, there are chemicals, such as wash solutions, deproteinizing reagents, conditioning reagents, buffers, diluents, precipitants, active ingredients, and other materials which are used to prepare the specimen samples. Additional reagents or systems may also be needed for the instruments to operate.
The sensors used in these instruments can be based on a variety of chemical principles, for example they may rely on spectrophotometry, potentiometry, amperometry, etc. Many, but not all, of the reagents are water based. Others may be lyophilized or powder reagents and may need to be reconstituted with water before use. Still others may be solvent based or in other forms. Because these reagents contain nutrients for microorganisms, microbial growth is frequently a problem, especially for commercially distributed products, which often require months or years of shelf life in order to be commercially practical products.
One subcategory of such instruments and chemicals are those which are used in the critical care area, where the analytical results must be obtained quickly, for example, when the patient is in the operating room or emergency room. These are used to measure such items as the concentration in the blood of such components as carbon dioxide, oxygen, total hemoglobin, sodium, potassium, chloride, calcium, lactate or glucose, and such physical properties as pH. In this environment it is especially important that the systems work properly, because of the need for personnel to quickly make decisions regarding diagnosis and treatment of the patient. This means that, among other things, the reagents must not become spoiled because of the action of microorganisms, and, therefore, it is customary to use microbicides (also called antimicrobial agents and preservatives) in these systems.